Line-splitting in high-resolution superconducting tunnel junction EUV detectors

We have developed high-resolution Nb-Al-AlOx-Al-Nb tunnel junction extreme ultra-violet (EUV) detectors. In the energy range between 25 and 70 eV, we have measured an energy resolution of 2.2 eV full-width at half maximum (FWHM), The energy resolution degrades significantly in the energy range between approximate to 80 and approximate to 230 eV where the Mb absorber is partially transparent and some of the photons are absorbed in the Al trap layers. We have for the first time observed a distinctly different response for photons absorbed in the Nh and the Al layer of the same junction electrode, We have modeled this effect with Monte-Carlo simulations of the charge generation process in superconducting multilayers.